if you are referring to the WIFI password.
first login to your modem's GUI http://192.168.254.254
then login using "user" (without the ") as your username and password
Click Wireless icon (beside Status icon) then Wireless Settings (below Home icon)
Update the SSID (Wifi name) and Pre-Shared Key (Wifi password)
(if wala yong SSID or Pre-Shared Key na field don sa Wireless settings, click mo yong Security katabi ng Wireless Settings)
then click Apply.
Restart the modem if necessary.